With a heat wave sweeping much of the United States, many Americans are undoubtedly wearing as little as possible, and all that bare skin may have effects beyond cooling. As the premise of the new indie film “30 Beats” or the steamy ice-cube scene from Spike Lee’s “Do the Right Thing” demonstrate, many people believe that sweltering temperatures have a tendency to push us into one another’s arms.

Do high temperatures really contribute to an increase in sexual activity?

It depends. The most concrete measure of rates of sexual activity is the seasonal pattern of birth rates. As it turns out, the numbers depend on where in the world you live. According to one literature review, in southern and tropical climates, births tend to decrease in the spring, indicating that conception was less common during the previous summer. Researchers postulate that deterioration of sperm quality during the hot summer months may depress fertilization success. Other research shows a decrease in testosterone levels – and therefore possibly sexual desire – in men during the same period. People living in cooler northern climes demonstrate the opposite pattern, with peak birth rates occurring in the spring – nine months after summertime.

According to condom-manufacturer Trojan’s “Degrees of Pleasure” survey, respondents living in the hottest areas, such as Miami, reported having more sex on average than their peers in areas such as Minneapolis and Seattle. Still, even Miamians might turn down a proposition during on the hottest days – according to the same study, 35 percent of Americans have said “no” to sex because of the heat.

Assuming pleasant-to-bearable heat, what might explain an increased interest in hooking up? Sweat may play a role, but not because of pheromones. As studies on a number of animal examples show, increased heat has a tendency to degrade these compounds.

But perhaps the answer isn’t as complicated as chemistry. With summer’s longer days, people spend more time outside, giving them more opportunities to interact with one another.

One last possibility: According research on “embodied cognition,” humans are primed to conflate temperature with emotional perception of relationships. Specifically, a paper by Matthew Vess of Ohio University suggests that, in many people’s minds, the concept of warmth is associated with intimacy.